Sadly they both sit in an awkward spot of being inferior to Emrakul, the Eons Torn yet just about as hard to cast
Blue's milling tends to come in two mechanical parts: spells that mill numerous cards once, and permanents, most often creatures, that can repeatedly mill smaller amounts of cards
Activating the ability that turns it into a creature while it's already a creature will override any effects that set its power and/or toughness to a specific number
Five mana is a little steep for aggro decks, but clearing a blocker and making an opponent lose life is kind of like giving Dalek Drone haste
Putting a lore counter on a Saga will usually cause its next chapter ability to trigger
And when the instance does arrive when the Extraction effect is relevant, you can enjoy the smug feeling of packing the perfect answer, without the opportunity cost that doing so usually incurs